Concern may be raised regarding the use of whole brain irradiation and its potential deleterious effect on neurocognitive testing. There have been reports on post-radiation neurocognitive testing in the setting of prophylactic cranial irradiation (PCI), which is whole brain fractionated RT commonly employed for patients with pulmonary small cell carcinoma. The standard whole brain PCI dose is 2.5 Gy x 10, considerably higher than the 2.0 Gy x 5 or 2.0 Gy x 10 schemes planned in the present study. Furthermore, patients in the PCI studies also received chemotherapy in addition to whole brain irradiation, and chemotherapy itself effects long-term NCF. In these PCI reports, if any neurocognitive decline was identified, it was modest, occurred within a short interval, e.g. 6-9 months, and improved. The investigators are thus proposing a 9-month follow up period for the 1st subject cohort (2.0 Gy x 5) before proceeding with the 2nd cohort (2.0 Gy x 10), although both cohorts will undergo NCF and QOL testing through 12 months.